This isn't necessarily focused at just PHP:
When designing/coding an application, try to avoid hardcoding any proper nouns in anything (variable names, file names, site 'structures', etc...). It can be a huge pain in the ass to go back and change them later.
Example (which just so happens to be bothering me at work):
Your company's name is hardcoded into file names, contact addresses, what have you (recent situation: company name was hardcoded as the default "other" category for equipment -- used throughout code & database).
....... what happens when/if your company changes name or gets bought?
Not sure if that makes any sense, but I've found keeping things vague or non-possessive saves a LOT of time, down the line.
If this still doesn't make sense, just code your stuff as if you were to design something completely generic, as to be sold to many different people. All branding, names, logos should be easily modified in one place and accept drop-in replacements.